hile the
Esoteric K-01 is most readily considered a digital-disc player, it goes beyond the
well-established feature set for such components -- far beyond. It begins with
spinning CDs and SACDs, progresses through the ability to decode digital data via its trio
of digital inputs, and continues on to the ways in which it can be used in an audio
system: either connected to a preamp or as a digital preamp itself. It has multiple
digital filters, three different upsampling levels, and two different output levels. You
can use it via single-ended RCA or balanced XLR outputs, turning the unused pair off
completely. You can specify different modes for its USB input and different levels for its
balanced outputs.

Price: $22,500
Warranty: Three years parts and labor with registration.

You get the picture. Other CD and SACD players end where
the K-01 begins. But such flexibility is no accident. It's the result of a calculated
ascendancy for the Esoteric brand. I've written a half-dozen reviews of Esoteric products,
beginning with the DV-50 universal player (which I purchased) and including the various
X-01 models (which I also purchased), and a pair of separates: the P-70 and D-70, and the
P-03 and D-03. None of those products settled for convention in terms of its feature set,
but none went as far as the K-01, which is really a product of this digital-audio age,
when file playback is nearly as ubiquitous as spinning discs.

In high-end audio, however, a jack of all trades is
oftentimes a master of none, and that's the perception a product like the K-01 must guard
against: flexibility and convenience over audiophile sound quality. No worries there --
the K-01 is the best-sounding Esoteric product I've heard, and its list of features could
make it the last digital product you'll ever own.

Let's start the discussion of the K-01's capabilities
with the spinning disc. Esoteric is well known for its VRDS transport mechanisms, which
clamp the disc in order to improve the laser's reading accuracy. The K-01 uses the latest
and greatest VRDS-NEO VMK-3.5-20S mechanism, among whose unique features is the use of
ceramic spindle bearings for smoother operation. This mechanism is massively overbuilt
compared to its off-the-shelf brethren, weighing almost 12 pounds. Also massively
overbuilt is the K-01's digital-to-analog converter section, which is based on that of
Esoteric's line-topping D-01. Like that digital-to-analog converter, the K-01's audio
circuit is completely dual mono -- right down to its eight AKM AK4399 DACs, which are mono
themselves, further lending to the player's quest for sonic purity. These can handle
incoming data at up to 24 bits and 192kHz, the current speed limit for native PCM data.
Circuit layout is done with utmost care. Analog and digital sections are physically
isolated within the K-01's chassis -- another Esoteric tenet -- and the player's
multi-level layout positions circuit boards to isolate signal-carrying circuits from the
unit's multiple power supplies.

Older Esoteric players
converted SACD's DSD data stream to high-resolution PCM, but not the K-01, which can
actually convert PCM to DSD if so desired, the AKM DACs decoding both natively. The
K-01 also upconverts at two different levels, double and quadruple the incoming sampling
frequency, and features a pair of digital-filter options: FIR, which Esoteric has included
in earlier units, and S_DLY. Knowing their particular technical characteristics is not
nearly as fruitful as simply listening with them (or without them -- both can also be
defeated), especially in conjunction with the K-01's upsampling.

Such flexibility can be daunting or merely inconvenient
to use, but the K-01's interface makes this process easy. Features of the more
set-it-and-forget-it variety are nested within the player's interface, while ones you will
want to change more often are only the push of a single button away, the results in both
cases displayed on the player's LED readout. So, for instance, if you decide to use the
K-01 as a digital preamp with an external clock and both a CD transport and computer
connected, it will take you a few moments to maneuver to the point within the interface to
turn on the K-01's volume control and clock link, while switching between connected
devices (or playing discs with the K-01) is just the push of the player's Mode button
away. While this button is not duplicated on the K-01's remote, if it were you would need
to have the player near your listening seat in order to see the display. It's obvious that
someone at Esoteric gave all of this close scrutiny, and it makes the K-01 simplicity
itself to use no matter your system configuration.

But there is a logical question that all of this
doodadery raises: which configuration is best? I'm pleading the fifth here, because the
upsampling and digital filters, for instance, all possess tradeoffs, as does the use of
the K-01 as your system preamp. But there are a few general conclusions that I can draw.
First, in the past, I was adamant about connecting Esoteric players balanced only. I not
only reasoned that paying for the redundancy of a fully balanced circuit, which the K-01
has, means that you should make use of it, but I heard definite sonic degradation when
those earlier products were connected single ended. The K-01 still sounds its best
balanced, but it remains the player I describe below when used single ended, which is a
roundabout way of saying that Esoteric seems to have addressed this issue with the K-01. I
could be very pleased using it either way.

The next feature to consider is direct connection to your
power amp, using the K-01 as the system preamp, albeit one that will accept only digital
sources. In theory, the K-01's digital volume control takes advantage of the AKM DACs'
32-bit resolution, causing no measurable degradation of the audio signal until you get
below a certain volume threshold. In practice, its use will depend on the quality of your
existing preamp and your system structure. With, for instance, the VTL TL-7.5 Series III
or Audio Research Reference 10, the two preamps with which I used the K-01 most, there was
no question that they made a clearly audible case for themselves, expanding the system's
capabilities in ways that were -- no surprise -- consistent with their sonic
personalities. In other words, both were better than no preamp at all.

Yet, if what I say about the K-01's sound resonates with
you, you will want to experiment with direct use. And while we analog diehards may decry
the fact that we can't play our records in such a system, Esoteric comes to the rescue
with a product from Italy that TEAC distributes in the US: the M2Tech Joplin, an
analog-to-digital converter that can accommodate LP playback -- and how. It has a wide
array of built-in EQ curves beyond RIAA, so you can play (and even record, if you have the
right hardware) your LPs. I hope to write about this unit at some future point in the
context of an article on high-res archiving of vinyl, for which it can also be used.

This leaves the question of the K-01's upsampling and
filters to consider, and here there is a more clear-cut answer, at least with some of your
CDs and files (SACDs are not affected, of course). I agree with Roy Gregory's conclusion in his
article on one-box CD/SACD playback (and the K-01 in particular): you will want to set
upsampling and then filter, if for no other reason than that the latter has a more
profound effect. Roy settled on "filter setting of FIR1 (variable cutoff point) and
ORG (or zero) upsampling." This was the combination of settings that maximized the
K-01's sonic capabilities, although there were certain CDs with which other filter or
upsampling settings worked somewhat better -- for instance, I preferred DSD upsampling for
the various Blue Note RVG reissues, whose thin, wiry sound benefited from the civilizing
that the DSD filter brought. And there were instances when pure preference at the moment
took over, and I thought that a different setting or combination was superior.

In the end, living with the K-01 and its innumerable
choices can be invigorating, but most serious listeners will eventually grow tired of this
novelty and settle into one combination. And if you don't, the K-01 will continue to
fascinate, as you really can take a sonic vacation with just a few adjustments.

f you've followed the trajectory of the Esoteric
brand, you know that designing and manufacturing advanced, robust digital players is
something Esoteric has been doing as a matter of course. But at the same time the company
has pushed itself, never settling for following a path it has already taken. The K-01 is a
product of this time, when digital requires more than simply spinning discs or playing
files. Both are de rigueur for the K-01, and if the preamp can be dispensed with,
all the better. But the K-01 is also proof of how far digital audio has progressed, both
in its do-everything approach as well as its sound. Long gone are the days of a
fundamental amusical character brought on by jitter or a deliberate softness meant to
compensate for this by (poorly) approximating analog. The notion that SACD players have to
make their reputations on their CD playback remains. No matter what anyone tells you, the
lowly, antiquated CD is still the dominant format for audiophiles here and now.

I was fortunate to use the
K-01 for an extended period of time, which gave me the opportunity to get to know it very
well. In sonic terms, it is neither assertive nor demure. Instead, it possesses musical
power (my term), which it displayed with all media that came its way -- CDs, SACDs and
files -- proving its worth no matter how it was used within the system. CDs were
exceedingly well resolved and singular, the K-01 neither compensating for perceived flaws
in the format nor relegating CD performance to a tier below its way with SACDs or high-res
files. By "musical power," I mean that its inherent drive and sense of forward
momentum were always obvious. However, they didn't overshadow the player's musical soul,
in the same way that the K-01's crushing bass never dominated its lithe, robust mids or
extended, airy treble. The K-01 had the uncanny knack of sounding detailed and substantial
as well as effortless and supple, toeing both sides of a very important sonic line.

In past reviews of multi-format digital players I've
compared different versions of the same recordings, which revealed how the sound of the
various discs (or, perhaps more accurately, the various masterings) differed, even
though the music was identical. There's something peculiarly enlightening about this
exercise, perhaps because it boils evaluation down to its very roots: one presentation
versus another, A versus B. No matter -- the K-01 made clear, for instance, that among the
versions of Getz/Gilberto I have -- something like six in total -- the SHM SACD
[Universal UCGU-9001] and K2 HD CD [LIM K2HD 036] sounded best. In this context,
"best" did not mean meatier in the bass or more relaxed in the treble -- did not
mean that any one or two sonic attributes were better, thus trumping the overall
presentation. Instead, it meant more complete, less compromised. The very first SACD
version of the Latin-jazz war-horse [Verve 314 589595-2], for instance, sounded clunky and
mechanical, as though the speakers' drivers were somehow misaligned, while the Mobile
Fidelity CD [MFSL UDCD 607] was drier and lighter, with less substantial bass. Most
significant, however, was the fact that the K-01 made these differences plain, proving
that CD can keep up with SACD -- when the CD has very good sound to begin with,
that is.

The K-01 was devoid of tonal quirks, those things that
help define a product's personality but grow tiresome over the months and years, making us
all the more susceptible to a change in sound seeming more significant than it really is.
This evenhandedness was also the case in terms of perspective, the K-01's soundstage being
neither forward nor recessed, although the player's sense of rhythm and drive gave it an
emphatic quality that some might consider forward, although it certainly was not in a
spatial sense.

If there was a sonic thrill from the K-01, it was in the
bass, which displayed impact, substance and, when it's on a recording, immense power. I
had a sense of this early on during my time with the K-01, but one addition to the system
made it all the more clear: the Wilson Audio Thor's Hammer subwoofer. I'll be writing
about it later in the year, and while its sheer size and weight put it comfortably in
behemoth category, it does so much more than simply extend the bass and pressurize the
room. With nearly all recordings, the Thor's Hammer just went about its business, but
every now and then a recording would offer up a surprise in the form of previously unknown
low bass. And it was often a recording I wouldn't suspect based on the music. One of these
was Natalie Merchant's The House Carpenter's Daughter [Myth America MA 1026], a
collection of folk music, some serene, some hard-edged and raw. It has a couple of cuts
with hidden bass, the sort with depth and power you won't experience without a sub like
the Thor's Hammer (and I know of no sub like the Thor's Hammer).

Of course, if the source can't reveal that bass, it
remains the proverbial tree that fell in the woods, but the K-01 wrested every last ounce
of it from the disc -- and any disc. On "Diver Boy," one of the grittier
numbers, the low-end growl punishes speakers, no matter the size of their woofers, but the
Thor's Hammer simply presented what came down the signal path, which began with the K-01.
Even on familiar discs, like Keith Richards' Main Offender [Virgin V2-86499] the
K-01 just seemed to reveal more of the rhythmic power underpinning the music, subwoofer or
not. I mention Main Offender so often in my reviews not because I never stop
playing it, but rather so that if you spot it at a music store or online you will take a
chance and buy it. If the music doesn't enthrall you, the sound will. Trust me on
this one -- buy it, cue up "Runnin' Too Deep" or "Words of Wonder,"
set the volume control a few ticks past the highest spot you usually listen, and prepare
to be amazed.

While the K-01 is surely capable of some amazement of its
own, it builds upon what Esoteric players have historically done well: reveal massive
amounts of musical detail, push the music along with a strong rhythmic foundation and
sense of momentum, portray musicians and singers with substance and dimension. Yet, my
memory of earlier Esoteric players tells me that the K-01 is clearly a further refinement
and extension of those significant sonic traits -- a matter of both more and better. No
component is for everyone -- or even for most listeners -- but it would difficult to use
the K-01 and not be impressed by its impossibly rich feature set, and it would be equally
difficult to hear it and not think that in some ways you can't do any better here and now.
It's that smartly conceived, that well built, that musically convincing.

ike the K-01, the Ayre DX-5 "A/V Engine"
($9950) is a feature-rich digital source. However, while the DX-5 plays CDs and SACDs, it
has DVD (both audio and video) and Blu-ray covered as well. As this indicates, the DX-5 is
also a video player, although the only time I use this feature is when I adjust its menus
or maneuver around a DVD. I don't consider the DX-5's ability to play DVDs and Blu-ray
discs a mere novelty, however. The high-res music on these discs can sound simply amazing
and some of it is truly special -- you won't be able to hear it with the K-01 unless it
has been downloaded. Of course, both players are also asynchronous USB DACs that are able
to decode data at up to 24 bits and 192kHz sampling frequency, and while the K-01 has
digital inputs other than USB, the DX-5 does not.

Like the K-01, the DX-5 is fully balanced; Charles Hansen
of Ayre considers this a cornerstone of his design philosophy. Unlike the K-01, the DX-5
uses an off-the-shelf mechanism from Oppo Digital that is not as substantial as the K-01's
VRDS NEO. The K-01 weighs at least three times as much as the DX-5, surely due to the
mechanism and thick brushed aluminum in which it's clad on every surface, and the DX-5
cannot match Esoteric player's preamp functionality -- or its clock-link facility,
adjustable upsampling and sheer luxe fit'n'finish. The Esoteric player is smoother and
quieter in operation as well, giving the K-01 all the precision and solidity of a BMW.

While these two players are multi-format digital
centerpieces, they also are reminders of how different companies approach similar problems
-- and attain vastly different sonic outcomes. Whereas the K-01 sounds unequivocally
detailed and powerful, the DX-5 is more modest, even laid-back in comparison, its high
resolution never overshadowing the unified, easy-going way it portrays music. While the
K-01's tonal character is largely neutral, the DX-5, as I pointed out in my review of it,
had no overt warmth to its sound, "although there was smoothness from top to bottom
along with a touch of treble sweetness." "These didn't so much take the sharp
edge off digital recordings," I observed, "as much as make it less of an issue
within the fabric of the music."

Highlighting the various regions of the sound produced
puts each firmly in the K-01's corner, as the DX-5 doesn't possess quite the upper-end
sparkle, the midrange bloom, or the low-bass grunt of the K-01. However, as everything
combines into the musical signal, the DX-5 shines. It resists such parsing into frequency
bands or qualitative traits, being more about the whole than the parts. Put another way,
while the K-01 sounds more impressive, the DX-5 makes very impressive music.

Put still another way, I prefer the K-01, as even
with the easy recognition of its superior particulars, it still brings everything together
in a musically consonant way. It's worth noting, however, that Ayre has substantially
upgraded the DX-5, now called the DX-5-DSD, and what those upgrades, which include a
change in DAC and master clock, bring to this comparison is anyone's guess -- I've not
heard one of the new units.

igh-end audio, especially the strata that the K-01
inhabits, often comes down not to what's definitively the best, which is impossible to
determine in any actual way, but rather what a particular listener wants from his audio
system. While we reviewers certainly attempt to argue that our tastes define a complete
and convincing analog of reality, each listener is an island unto himself. His ears --
along with his tastes -- must be convinced before the checkbook will come out.

There is no convincing needed regarding the K-01's
feature set -- it's more vast than that of any single-box digital source I know of. In
fact, at the very least, you'd need both a very capable DAC and CD/SACD player to equal
it, with basic digital-preamp functionality still not accounted for. But strip the K-01 of
its user niceties and what you are left with is the sort of sonic performance that defines
high-end audio: playback that reveals the distinctiveness of each CD, SACD or file in a
fully resolved and powerfully real way. If substance, impact and sheer resolving power are
your personal sonic touchstones, this is a player you must hear.